Automatic choke for carburetors



June 22,1937. G, M, BICKNEL 2,084,607

AUTOMATIC CHOKE FOR CARBURETORS Filed March 25, 1933 I 4 Sheets-Sheet l GEORGE M. BICKNELL INVENTOR ATTORNEY June 22, 1937. G. M. BICKNELL 2,034,507

AUTOMATIC CHOKE FOR CARBURETORS Filed March 25, 1933 4 Sheets-Sheet 2 GEORGE M. BICKNE LL INVENTOR A TTORNE Y June 22, 1937.

4 SheetsSheet 7.4

. Filed March 25, 1933 i, v 7 GEORGE M. BICKNELL I A TTORNEY.

Patented June 22, 1937 UNITED STATES.

PATENT OFFICE 2,084,607 AUTOMATIC CHOKE FOR canmmnroas George M. Bicknell, St. Louis, Mo., assignor to Carter Carburetor Corporation, St. Louis, Mo., a corporation of Delaware This invention relates to carburetors used in connection with internal combustion engines, and more particularly to the automatic control of the air to fuel ratios of charges in accordance with the requirements of an engine.

It is an object of this invention to produce an improved carburetor capable of automatically forming charges of air and fuel upon which an internal combustion engine will operate eiiicient- 1o ly at various atmospheric or engine temperatures.

It is a further object of this invention to provide a means to supply comparatively rich charges, which are cold engines.

15 It is a further object of this invention to provide a means of immediately and definitely reducing the comparative richness of the starting mixture the moment an engine begins to operate under its own power.

Other objects and advantages will appear from the following description and claims, .taken in connection with the accompanying drawings in which like reference numerals refer to like parts.

Figure l is a somewhat diagrammatic view showing an elevation of the carburetor mounted m an engine manifold, with parts shown in section and others broken away.

Figure 2 is a side elevation of the carbure shown in Figure 1, parts being shown in section and others broken away.

Figure 3 is a vertical sectional view of the carburetor, the section being taken along the line 3-3 of Figure 2, looking in the direction of the arrows.

Figure'4 is a plan view of the carburetor and engine manifold pipes shown in Figures 1 to 3.

Figure 5 is a sectional view taken along line 6-6 of Figure 1 showing the thermostatic coil mounted on theexhaust manifold.

The reference numeral I indicates the lower half or main body of the carburetor. This lower half is provided with a flange 2 by means of which it is attached by stud bolts 3 to the intake v riser. of an internal combustion engine. The

5 upper half 6 of the carburetor is formed as a separate casting and is suitably fastened to the lower half by means of screws 6.

The two halves of the carburetor form a downdraft mixing conduit extending therethru, comprising air inlet l, air chamber 8, mixing chamber land discharge outlet ll.

The air'inlet I is controlled by choke valve ll "which is carried on shaft l2. The fuel for normal to the, mixing conduit 1 into the primary speed ope'ratiomis supp 55 thru nozzle 1': which required in the starting of venturi near its most restricted section. The primary venturi discharges into the secondary venturi l5 and the secondry venturi discharges into the main venturi l6 as indicated in Figure 1.

The discharge of the mixture from the carburetor is controlled by throttle valve I! carried on shaft I8, this shaft being arranged as with a lever l9 as shown in Figure 2 for manual operation. The fuel for low speed operation, is supplied to the mixing conduit thru port or nozzle 20 as shown in Figure 1. lit will be seen that this port is bisected by throttle valve I! when it is in closed position. Instead of the slot 20, it willbe understood that two separate ports interconnected with the idle tube 2| may be used.

Fuel is supplied to the nozzle 20 by means of idle tube 2|, connecting passages 22-23, calibrated and restricted passage 24, passage 25 and metering jet 26. Fuel to the main nozzle is also supplied from jet 26, passage 25 and chamber 21 which surround tube 28. It will be seen that both the main nozzle l3 and the idle nozzle 20' i receive fuel from jet 26 and that they are interconnected by the calibrated passage 24. The jet 26 is controlled in accordance with the position of the throttle by means of metering rod 29. The jet 26 takes its fuel from chamber 30 in which the fuel is maintained at a constant level AA by float 3| and needle valve 32. Fuel is supplied in a conventional manner to needle valve 32 thru connection 33 by the usual fuel pump. or gravity tank.

The accelerating pump 34 is operated from rocker arm 35 which in turn is operated by the throttle valve thru link 36 and operating arm pump have no relation to the present invention and are not shown.

To control the choke valve position and therefore-the quality of the mixture in accordance with the temperature of the engine and also to control the quantityof air as required according to the various requirements of the engine, a coiled spring thermostat 33 of conventional bimetallic construction is provided and enclosed inv case 33 to protect it from the fan blast. It will be seen that choke valve II is eccentrically mounted on the shaft l2, thereby having a tendency to open as vacuum is created within the mixing conduit. v

The outer end of the thermostatic coil is anchoredtothelmnsing" bymeansofa'stud' arm 43,the set screw holding it in adjiusted position. The choke valve l I is controlled by the thermostatic coil thru shaft 42, arm 43, link 44 and arm.

45. Arm 45 being adjustably aflixed to shaft l2 as shown in Figure 4 by set screw 46.

To provide additional fuel to form a starting mixture for a coldengine, an auxiliary jet 41 controlled by lifting needle 48 has been provided as shown in Figure 3, arm 49 being pivotally mounted on shaft [2 is provided with a lug 50, which, when the choke valve is in a closed or cold-starting position is contacted by lug 5| of cam 52 which is rigidly fixed toshaft J12. It will be seen, therefore, that a clockwise rotation of the choke shaft l2 in Figure 3 which is a 0105- ing motion of valve ll will also cause a clockwise motion of arm 49 which in turn efiects the lifting of needle 48. It will be further noted that this arrangement allows a free counterclockwise motion of shaft 12 whereupon needle 48' will return to its seat by reason of spring 53.

To immediately admit additional air and therefore reduce the richness of the charge the moment an engine begins to fire and operate under its own power; a suction operated plunger valve 54 extending into air inlet 1 and into a notch 55 in choke valve H has been provided, as indicated in Figures 1 and 4.

Referring toFigure 1 this valve on piston 54 is shown in section slidably mounted in cylinder 56 and held normally in the position shown by spring 51. A conduit 58 and passages 59 and 60 connect cylinder 56 with the mixture discharge outlet below the throttle valve.

' brated so as to hold piston 54 in the position shown during cranking, and that the vacuum created below the throttle at the first fire of an engine will cause the piston to recede from air inlet 1 to a point where the outer end of piston 54 is flush with the wall of the air inlet, thus admitting air thru notch in valve ll.

The operation of the device shown in Figures 1 to 5 is as follows:

Upon starting a cold engine in an atmospheric temperature requiring a comparatively rich starting mixture; the choke valve will be in a closed position, with the tension in the thermostatic coil spring tending to hold it closed. The design r of the thermostatic coil is such. as to respond 'to thermal conditions to the correct degree for its operation of the choke valve and to permit the choke valve II to open in response to suction in the air chamber 8. I

' In cold starting, the choke valve being in a closed position, needle 48 will be in the lifted position admitting fuel thru auxiliary jet 41.

As the motor fires and begins to operate under its own power, sufllcient suction will be created below the throttle valve to withdraw piston 54 from notch 55 in valve II. It will be understood that the tension of spring 51 is so calibrated as to prevent piston 54 from withdrawing by reason of any vacuum which may be created during cranking of an engine However, its tension is readily overcome by vacuums created by an engine running under its own power.

- As the engine continues to run and particularly if the speed is increased the vacuum created will have a tendency to open choke valve II by reason of its oil? center location on shaft I2 against the coiled spring action of the thermostat, thus operating as an air valve.

As the temperature increases in the exhaust warmed up sufiiciently to cause the choke valve to be held wide open, and thereafter, during the continued operation of the engine, further increases in the temperature, or variations in the suction, have no efiect on the position of the choke valve, and the carburetor operates on what is generally known as the plain tube principle.

The invention is not limited in details to the structure shown but may be modified in various respects as will occur to those skilled in the art and the exclusive use of all such modifications that come within the scope of the appended claims is contemplated.

I claim:

1. In a-carburetor, means forming a mixing conduit having an air inlet passageway, a choke 2. In a carburetor, means forming a mixing conduit, a suction operable choke valve controlling the admission of air to said mixing conduit and having a recess, a throttle valve controlling the discharge of mixture from said conduit, and an auxiliary air admitting valve controlling said recess and constructed and arranged to be controlled by suction posterior to the throttle for admitting air to said mixing conduit independent of the position of said choke valve.

3.-In a carburetor, means forming a mixing conduit, a throttle valve and a choke valve in said mixing conduit, a notch in one side of said choke valve, apiston projecting into said notch, and means comprising a suction connection, to a point in said mixing conduit posterior to said throttle for operating said piston.

4. In a carburetor, means forming a mixing conduit and a fuel reservoir, a choke valve and a throttle valve in said mixing conduit, said choke valve being constructed and arranged'to be moved toward open position by suction, a heat responsive device for closing said choke valve when the temperature is low, main and auxiliary fuel supply devices for supplying fuel from said reservoir'to said mixing conduit, means for leaning but the mixture in response to increases in the suction posterior to the throttle, and means for discontinuing the auxiliary supply of fuel when the choke valve is moved to open position.

5. A carburetor comprising a casing having a mixture passageway therethrough, said passageway having an inlet and an outlet, a valve in said a portion of said valve being cut away to provide a by pass, a second valve mounted independently of said first valve and capable of controlllngflow 75 through said by pass,-and a heat responsive device for controlling one of said valves, said second valve being exposed to and operated by suction existing in the outlet of said mixing passageway.

6. In a carburetor a mixing conduit, a choke valve and a throttle valve therein, main and auxiliary means for supplying fuel to said conduit, and means for supplying'auxiliary air to said conduit past saidchoke valve when closed, said last mentioned means being controlled by suction posterior to said throttle valve and said auxiliary fuel supply means being controlled by said choke valve, said auxiliary air and fuel means being constructed and arranged so that said auxiliary air supply is restricted and said auxiliary fuel supply is operative when said choke valve is closed and the engine is being cranked and said auxiliary air supply is open when the engine fires, said auxiliary fuel supply being restricted as the choke valve opens.

' GEORGE M. BICKNEIL. 

